Obama on his way to announce Biden

Tribune photo by Nuccio DiNuzzo

Democratic presidential candidate Sen. Barack Obama makes his way to the podium to introduce Sen. Joe Biden as his choice for running mate during a rally in front of the Old State Capital in Springfield , Ill.

Democratic presidential candidate Sen. Barack Obama makes his way to the podium to introduce Sen. Joe Biden as his choice for running mate during a rally in front of the Old State Capital in Springfield , Ill. (Tribune photo by Nuccio DiNuzzo)

Democratic presidential candidate Sen. Barack Obama makes his way to the podium to introduce Sen. Joe Biden as his choice for running mate during a rally in front of the Old State Capital in Springfield , Ill.